Atmospheric Deposition of Nutrients Shifts Carbon Capture and Storage Trends in Freshwater Tropical Lakes in India

Abstract

An understanding of ongoing changes in biogeochemistry of carbon (C) as influenced by increasing atmospheric deposition (AD) of nutrients is important for integrated water resource management and for exploring options for balancing C sink and fluxes. To determine whether AD-nutrients would increase phytoplankton production and catchment carbon flushing in lakes, we analyzed NO 3 , NH 4 and PO 3 4 in atmospheric deposits, microbial biomass and activity in catchment, nutrient and dissolved organic carbon (DOC) in runoff and, phytoplankton production and sediment-C in six freshwater lakes from 1999 to 2008. Although N: P stoichiometry of AD did not change over time, there was over 1.5 fold increase in AD-NO 3 , NH 4 and PO 3 4 overtime. Microbial biomass and activity in catchments and, DOC and nutrients in runoff increased consistently over time. Lake nutrients, DOC, gross primary productivity, chlorophyll a biomass and sediment-C also showed positive relationship with AD-nutrients. The study indicates that rising input of AD-nutrients steer freshwater lakes towards greater productivity, whereas such inputs in catchment enhance microbial processes and consequently runoff DOC flush and the-coupled effects of these may cause long-term shift in water quality and C balance of these ecosystems.

Variations of water quality indicators in closed tropical freshwater systems towards selected climatic and anthropogenic disturbances

“…Extreme precipitation events (which is increased in the region during recent years) have enhanced N loading from terrestrial watershed to the lakes consisting of vegetational debris and animal waste. Increase in nitrate concentration can also take place as a result of anthropogenic disturbances andenhanced microbially fixed-N (Pandey and Verma, 2004). A remarkable observation in the study is the amplification of N:P ratio i.e.…”

Anthropogenically Induced Shifts in N:P:Si Stoichiometry and Implications in Ganga River

“…Earlier studies have shown a consistently rising trend in AD input and lateral transport of nutrients to lakes and rivers in many parts of India. 5,8,22 Intensive studies conducted in the middle segment of Ganga River 5,6 showed that AD input contributes, almost on similar spatiotemporal scale, large fluxes of DIN and DRP as direct deposition and through land surface runoff to the river.…”

“…6 In seasonally dry tropical regions of North India, extensive landscape transformation accompanied by massive use of fertilizers with urban-industrial factors drastically influences the aquatic ecosystem functioning. 7,8 Water bodies with naturally low N or P are highly sensitive to the external input of these nutrients. 9 The N:P ratio (referred to as Redfield ratio) is an important indicator of which nutrient is limiting the phytoplankton growth.…”

“…6 In seasonally dry tropical regions of North India, extensive landscape transformation accompanied by massive use of fertilizers with urban–industrial factors drastically influences the aquatic ecosystem functioning. 7,8…”